Thread cutting device for sewing machines



March 5, 1968 K. HEDEGAARD 3,371,633

THREAD cuw'rme DEVICE FOR SEWING MACHINES Fild A ril's, 1966 6 Sheets-Sheet 1 I l i I I l i I l I I Fig.1

March 5,1968 Y K. HEDQEGAARD 3,371,633

THREAD CUTTING DEVICE FOR SEWING MACHINES Filed April 5,. 1966 6 Sheets-Sheet 2- INVENTOR.

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' lrklJfs/v [mm 4440 BY A1424 ea r A 77'0 R NE) March 5, 1968 K. HEDEGAARD THREAD CUTTING DEVICE FOR SEWING MACHINES Filed April 5. 1966 6 Sheets-Sheet 4 Fig. 72

lrmz. RAr/I A r r0 2 N5) March 5, 1968 K. HEDEGAARD 3,371,533

THREAD CUTTING DEVICE FOR SEWING MACHINES Filed April 5, 1966 v 6 Sheets-Sheet 5 Fig.1.?

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THREAD CUTTING DEVICE FOR SEWING MACHINES Filed April 5, 1966 6 Sheets-Sheet 6 I N VEN TOR Ire/s rev #5056 M20 Ira 2L. 2A7?! United States Patent 9 Claims. of. 112 2s2 The present invention relates to thread-cutting apparatus for sewing machines of the type comprising means for the withdrawal of a suificient length of upper (needle) and lower (looptaker or bobbin) thread prior to the severing of the threads by the cutting device after the completion of a sewing operation.

As is well known, it is necessary, before the cutting or severing of the needle and bobbin threads at the end of a sewing operation of a sewing machine, to withdraw a suificient length of the threads from the lower and upper thread supplies to ensure the safe initiation of the stitchforming operation upon the commencement of a subsequent sewing operation by the machine. For this purpose, it has become known to provide a special thread-withdrawing device operative prior to the initiation of the thread-cutting action proper.

It is furthermore known, for this purpose, to fit the cutting knife or the like provided for the severing of the threads with thread-withdrawing means disposed adjacent to the knife edge and capable of feeding or displacing the withdrawn threads towards said knife to cutting position prior to the initiation of the thread cutting operation proper.

These and other known thread-cutting devices are suitable only for embodiment in sewing machines of the type being substantially devoid of any work feeding means or other auxiliary devices occupying the space below the stitching plate and adjoining the stitching point of the machine, for the reasonthat, aside from the considerable bulk involved or number of parts required, little or no space is ordinarily available in most machines within the region in the vicinity of the stitching point for the mounting of both the thread-withdrawing and thread-cutting devices required to ensure a safe and reliable cutting of both the needle and bobbin threads at the end of a sewing operation.

Accordingly, an important object of the present invention is generally to simplify the thread-withdrawing and cutting operations of a sewing machine by substantially dispensing with a number of auxiliary devices or elements below the stitching plate and in the vicinity of the stitching point of the machine which may be of standard or I conventional design or construction.

Another object of the invention is the provision of a thread-withdrawing and cutting device of the referred .to type by which the withdrawn threads are simultaneously fed or displaced to an operative position adjoining the cutting device proper, to afford a safe and reliable cutting or trimimng of the threads.

A more specific object of the invention is the utilization of the looptaker or elements thereof as means for withdrawing the threads and to guide the withdrawn threads to a position for cutting by the cutting device proper of the machine.

The invention, both as to the foregoing and ancillary objects as well as novel aspects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this specification and in which:

FIG. 1 is a front elevational view, shown partly in section, of a column-type double lockstitch sewing machine embodying thread-cutting mechanism constructed in accordance with the principles of the invention;

FIG. 2 is an enlarged longitudinal sectional view through the column of the machine according to FIG. 1 with unessential parts being omitted from the drawing;

FIG. 3 is a partial view more clearly showing the drive mechanism for the thread cutter;

FIG. 4 is a similar partial view more clearly showing the mechanism for the rotation of the bobbin case forming part of the thread cutter of the invention;

FIG. 5 is a partial perspective view of the stitching tools and thread-cutter of the machine of FIG. 1, shown in the position of the cutter prior to the cutting of the threads;

FIG. 6 is a perspective view similar to FIG. 5, show ing the cutter in the retracted or inoperative position;

FIG. 7 is another detail view, similar to FIGS. 5 and 6, showing the looptaker in the position immediately prior to the casting ofi? of the needle-thread;

FIG. 8 is an enlarged perspective detail view of the rotation-restraining member of the bobbin case utilized as an operative part of the thread-withdrawing mechanism of the invention;

FIG. 9 is a detail view of the thread-cutter per se shown in the inoperative position or during a sewing operation;

FIG. 10 shows the cutter according to FIG. 9 in the operative position or during the carrying out of a threadcutting operation;

FIG. 11 is a partial front view, showing the parts below the stitching plate of a chainstitch sewing machine embodying thread-cutting means in accordance with an alternative embodiment of the invention;

FIG. 12 is a plan view taken on line XIIXII of FIG. 11;

FIG. 13 is a sectional view taken on line XIIIXIII of FIG. 11;

FIG. 14 is a view similar to FIG 13, showing the chain-stitch looptaker in the thread-Withdrawing position;

FIG. 15 is an enlarged bottom view of the thread-cutter according to the chainstitch embodiment shown in FIG. 11;

FIGS. 1618 are three-dimensional diagrammatic views of the chainstitch looptaker of FIG. 11 in the normal, the thread withdrawing, and cutting positions, respectively; and

FIG. 19 is a wiring diagram illustrating the control of the needle position during the thread-withdrawing and cutting operation in accordance with the invention.

Like reference numerals denote like parts throughout the different views of the drawings.

With the foregoing objects in view, the invention involves essentially the provision of releaseable coupling or transmission means operably connecting a thread-carrying element of the loop taker of a sewing machine with the thread-cutting mechanism, whereby to displace said element, during a thread-withdrawing and cutting operation, in a direction opposite to or away from its normal position or operation during a sewing operation, in such a manner as to withdraw a sufiicient amount of bobbin as well as needle thread and to feed or present the withdrawn threads to the cutting device proper of said mechanism prior to the carrying out of the threadcutting operation.

In this manner, that is, by the utilization of the looptaker as a means for effecting the thread-withdrawing and catching or guiding operations, it has become possible for the first time to equip .a great number of sewing machines with a built-in thread-cutting device, by reason of the fact that the thread-cutter per so may now be mounted in a position being ordinarily obstructed by the looptaker element effecting the thread-withdrawing operation, the cutter being freed temporarily by the displacement of said element during the thread-withdrawing operation or cycle. In other words, the provision of a threadcutter will now be enabled in machines in which normally no or insufiicient space is available for the mounting of the thread-cutting parts or elements below the stitching plate of the machine.

A further advantage of the invention is due to the fact that additional parts of the loop taker may be utilized as transmission or actuating element for the thread-cutting operation, in a manner as will be further described in the following.

As an example, in the embodiment of the invention as applied to a lo'ckstitch sewing machine having a rotary looptaker wherein is frictionally mounted a bobbin case containing the looptaker thread and being restrained against rotation by the looptaker by a stop member engaging a stationary abutment, the bobbin case is advantageously utilized as a thread-withdrawing means by rotation through a predetermined angle in a direction opposite to the direction of rotation of the looptaker, said stop member being furthermore utilized as a means to guide the withdrawn bobbin thread as well as to catch the needle-thread during the initial operating period of the thread-cutting device or to present the threads to the cutter proper preparatory to the final cutting operation. In other words, the bobbin case is rotated to a sufficient extent prior to the cutting operation, to withdraw an adequate length of bobbin thread as well as of the needle thread, the latter being seized by the stop member of the bobbin case while being drawn about the looptaker and tensioned by the thread-takeup of the machine, whereby both threads are guided .and fed towards the thread cutter proper. At the same time, the stop member is moved out of the way of the normally obstructed thread cutter. In order to enable the latter operation, that is, the With drawal of both the looptaker and needle threads and the positioning of the withdrawn threads in proper cutting position, the needle is automatically stopped, at the end of a sewing operation, in the lower dead center position and is operated from said lower position to its upper dead center position synchronously with the thread-withdrawing and cutting cycles or operations, to thereby cause the needle thread to be drawn about the looptaker and to be seized by said stop member, in the manner described by and further understood from the following.

In the case of a machine of the type including an opening finger or the like, to intermittently release the bobbin case so as to enable the escape of the needle-thread loop from the bobbin case stop and abutment members, the invention may be carried into effect in an especially advantageous and simple manner by utilizing said finger, being rotatively mounted for this purpose about the looptaker axis, as a bobbin case rotating means in operative connection with the thread-cutting mechanism, in the manner :as will become further apparent from the following description of the drawings.

In the embodiment of the invention as applied to a double-chainstitch sewing machine having a thread-carrying looptaker hook subjected, in a known manner, to a composite movement about a pair of axes at right angle to one another for the production, respectively, of both needle-loop seizing and casting olf movements, as well as of needle-avoiding looptaker movement, an especially simple construction of the thread-withdrawing and cutting device according to the invention is obtained by movably mounting the shaft or spindle forming one of the oscillating axes of the looptaker operating mechanism and operably connecting the same with the transmission or control devices of the thread-cutter.

In this manner, the chainstitch looptaker is displaced, during a thread-withdrawing and cutting operation or cycle, from a normal operating (sewing) position, in such a manner as to withdraw a sufiicient length of looptaker and needle thread, while providing adequate space for the mounting of the cutting device proper.

More particularly, according to an especially advantageous arrangement in the case of a chainstitch machine, the shaft of the looptaker operating mechanism which is parallel to the looptaker hook is carried by an oscillating support or member at a distance from the fulcrum of said member, whereby to enable the thread-withdrawing operation to be achieved simply by rotation of said member, resulting in turn in a displacement of the looptaker in a direction normal to its lengthwise dimension and withdrawing of the threads, in the manner as will become further apparent as the description proceeds in reference to the drawings.

Referring more particularly to the embodiment of the invention according to FIGS. 1-10, there is shown a column type lockstitch sewing machine of generally conventional design comprising a head 1, 'FIG. 1, an overhanging arm 2, an upright 3, a base plate 4, and a worksupporting column 5. The main drive or armshaft 6 of the machine being journalled in the arm 2 operates, in a known manner and by way of a crank 7 and link 8, the reciprocating needle bar 10 mounted in a frame or carrier 9 and supporting a needle 11. Besides, the armshaft 6 serves to drive, by way of a belt or elastic chain 12, a further drive shaft 13 journalled below the base plate 4 and serving to drive the vertical looptaker shaft 19, FIG. 2, by way of a first gear pair 14, 15, an auxiliary shaft 16 and a bevel gear pair 17, 18, the looptaker 20 being secured to the upper end of the shaft 19.

Frictionally supported within the looptaker 20, by means of the usual cylindrical bearing rib engaging an internal raceway in the looptaker, is the bobbin case 21 which may consist of an inner and an outer part and which contains the lower or bobbin thread cooperating with the needle thread in a known manner, to form lockstitches in the work being operated on. The bobbin case 21, FIGS. 5-8, is fitted with a first stop 22 having an abutment face 36 adapted to engage a fixed stop 35 fast on the column 5, or stitching plate 33, to restrain the bobbin case against rotation by the looptaker, and a second stop 23 cooperating with an adjustable opening finger and thread-withdrawing device 40, in the manner to be described presently, stop 23 having an opening 24 from which emerges the bobbin thread 25 from the case 21.

Further journalled in the column 5 coaxially with the looptaker shaft 19, FIG. 2, is a hollow shaft 26 the lower end of which carries a bevel gear 27 being continuously driven in a manner well known (not shown). Secured to the upper end of the shaft 26 is a friction wheel 28 arranged in cooperative driving relation, through its friction coating 29, with the teeth of a work feedwheel 31. The latter projects through a slot 32 in the stitching plate 33 secured to the column 5 and in turn, cooperates with a further feedwheel 34, FIG. 5, mounted upon the head 1 of the machine for feeding the work to be operated on in a manner well known.

As described hereinbefore, the underside of the stitching plate 33 carries a stop 35 being engaged, during operation of the machine, by the face 36 (see also FIG. 8) of the stop member 22 upon the bobbin case 21. The stop member 22 is furthermore formed at the side opposite to the wall or face 36 with a thread-catching nose or guide 37 which gradually merges in the downward direction into a guide groove 38 extending along the underside of the member 22 up to the abutment wall 36.

In order to release the stop member 22 from the stop 35 during the instants of passage or escape of the loop formed by the needle-thread 39 passing through the needle 11, there is provided the opening finger 40 operable against the stop 23 of the bobbin case 21. Finger 40 is secured to a carrier 41 encircling an eccentric 42 which is carried by the looptaker shaft 19, FIG. 2. The carrier 41 is fitted with a fork 43 engaged by a projection 45 of an oscillating member 44 secured to the upper end of a further hollow shaft 46 journalled in the column coaxially with the looptaker shaft 19.

The operation of the finger 40 is effected in a known manner through the eccentric 42, rotating together with the looptaker shaft 19, by the carrier 41 being deflected during the sewing operation about the relatively stationary projection 45. As a consequence, the finger 40 engages, during each revolution of the eccentric 42, the stop 23, whereby to cause a release of the member 22 and to allow of ready passage and withdrawal of the needlethread loop 39.

Secured to the lower end of the shaft 26 is a gear 47 meshing with a further gear 48 mounted below the base plate 4. A ball and socket element 49, FIG. 4, provided in the gear 48 connects, by Way of a link 50, with one end of a double-arm lever 51 rotatively mounted upon a longitudinally displaceable control spindle 52 (see also FIG. 1) so as to be displaceable by but freely rotatable in respect to said spindle. The remaining end or arm of the lever 51 carries a guide pin 53 adapted to engage, upon displacement of the spindle, a guide groove 54 of a con-- trol eccentric or disk 55 mounted upon the shaft 16. A tension spring 56 connected to the link 50, on the one hand, and to the frame of the machine, on the other hand, serves to urge in the disengaged position of the pin 50, the lower edge 57 of the member 44 against an abutment or projection 58 upon the column 5, as shown in FIG. 6.

Secured to the spindle 52, that is, axially displaceably mounted below the base plate 4, is a setting ring or collar 59, FIG. 1, one side of which is engaged by an end of a compression spring 60 encircling said spindle, the opposite end of said spring engaging a sleeve or collar 61 diplaceably mounted upon the spindle 52. Collar 61 is in turn, engaged by the fork-shaped arm 62 of a bellcrank control lever 63 disposed below the base plate 4. Jointed to the remaining arm of the lever 63 is a pull bar 65 the lower'of which may be connected to a foot pedal 3 .or the like control member (not shown).

Further secured upon the spindle 52 is a stop or abutment sleeve 66 whose front end 67 is engaged by a blocking lever 68. In order to prevent the locking or jamming between the lever 68 and the surface 67, the latter is formed with a chamfere-d edge as at 69. The lever 68 is rotatively supported upon the drive shaft 13 and urged against the side of a friction ring 71, fast on and rotating with the shaft 13, by the action of a compression spring 70 encircling said shaft and engaging said lever, on the one hand, and the frame of the machine, on the other hand.

A further compression spring 72 encircling the spindle 51 and engaging the setting ring 59, on the one hand, and the frame of the machine, on the other hand, serves to urge the spindle 52 towards the right or limit position as shown by FIG. 1.

Mounted upon the looptaker shaft 16 is a further control eccentric or disk 73, FIGS. 1 and 3, having a groove 74. A further double-arm lever 75 rotatively and axially displaceably supported by the spindle 52 has its arm 76 fitted with a guide pin 77 adapted to engage the groove 74 while the remaining arm 78 of the lever 75 carries a pin 79 engaging the fork-shaped end of a further doublearm angular lever 81 mounted below the base plate 4, the opposite and equally fork-shaped end of which engages a pin 84 secured to the lower end of a pull rod 83.

The latter is displaceably mounted in the column 5 in' the vertical direction and carries at its upper end a pin 85, FIGS. 9 and 10, engaging each of the guide slots 86 and 87 of a pair of scissors or shearing parts 88 and 89 of a thread-cutter 90. The shearing part 88 is jointed to the column 5 by means of a pivot pin 91, while the shearing part 89 is jointed to the part 88 through a pin 92. The parts 88 and 89 terminate in the cooperating shearing or trimming blades 93 and 94, respectively. The guide slots 86 and 87 are shaped in such a manner as to cause, during the vertical displacement of the rod 83 and, in

turn, of the pin the two shearing parts 88 and 89 to be operated into and out of cutting engagement, to thereby close and open the blades. 93 and 94 of the threadcutter, in the manner as will appear from the description of the operation of the thread-cutter as follows.

The sewing machine is driven by a motor equipped with a stoppage device to alternately arrest the machine in the needle down or up positions. Such a device, being well known per se and shown for instance by US. Patent 3,224,543, may consist of a coupling motor controlled by a contacting device 95, FIG. 19. The contacting device comprises a contact disk 95a driven by the main drive shaft 6 of the machine and a pair of cooperating sliding contacts or brushes 95b and 950 spaced by about The electrically conducting peripheral surface of the disk 95a is interrupted by an insulating segment 95d being sequentially engaged by the brushes 95b and 950 during rotation of the shaft 6, or operation of the sewing ma chine. The contact disk 95a is connected via a further brush and slip ring 95a to a coupling electromagnet 96 which may be embodied in the coupling motor in the manner shown and described by the afore-mentioned patent, to effect a re-starting of the motor after the latter has been arrested at a point other than the points determined by the segment 950. by release of the main controller at the end of a sewing operation.

The electromagnet 96 may be connected to a direct current source not shown via the brushes 95b and 95c of the contact device, the contact 97a or 97b of a changeover switch 97 and a control switch 98. The latter is operatively connected with the foot pedal or the like control device for the operation of the machine (not shown) such as to be closed upon the machine being stopped at the end of a sewing operation (position shown in FIG. 19). The change-over switch 97, FIG. 1, on the other hand, is arranged below the base plate 4 of the machine to be operated by an actuating element 99, FIG. 11, fast on and displaceable with the spindle 52, to change from contact 97a to 97b upon displacement of the spindle towards the left at the initiation of a thread-cutting operation.

In use, while the sewing machine is still in operation, the pull rod 65, FIG. 1, is operated, before the completion of the sewing operation, in the example shown, in the downward direction by the foot pedal or the like control device mentioned. As a consequence, the spring 60 upon the spindle 52 is tensioned by the fork 62 and collar 61. With the shaft 13 continuing to rotate the lever 68 engages the spindle 52 by virtue of the torque thereon applied through the friction ring 68, whereby to prevent axial displacement of the spindle 52 by the lever 68 engaging the stop 66. On the other hand, the spring 60 remains tensioned, to store the order or control action by the lever 63.

If the sewing machine is now arrested, upon the completion of the sewing operation, the contact device 95, due to the closing of switch 98, FIG. 19, initiates a renewed rotation of the shaft 6 until the insulating segment 95d assumes a position opposite to brush 95b. During this operation, a current flows through the closed switch 98, the change-over switch 97, contact 97a, brush 9512, contact disk 95a, brush 95a and electromagnet 96. As a consequence, the latter is energized and actuates in a known manner the coupling motor, whereby the re-start rotation of the arm shaft 6 and contact device 95.

As soon as the disk 95a reaches the position shown in FIG. 9, the current through the circuit is interrupted by the segment 95d, whereby to deenergize the electromagnet 96 and to stop the motor with the sewing machine at a point coinciding with the lower dead center position of the needle 11. Shaft 13 is now caused to rotate by a slight amount in the opposite direction by virtue of the elastic energy stored in the belt 12 at the intsant of stoppage of the machine. The slight return movement of the lever 68 resulting therefrom releases it from the surface of the stop 66, whereby to cause the spindle to be operated towards the left by the action of the tensioncd spring 60 and to cause the lever 68 to become fully disengaged from the member 66 by the chamfered outer section 69 of the latter, in a manner readily understood. Alternatively, the machine may be first stopped and the lever 63 then operated to displace the spindle 52, in which case the storage spring 60 may be dispensed with.

As a result of the displacement of the spindle 52, the guide pins 53 and 77 FIGS. 3 and 4, enter the corresponding grooves 54 and 74 of the control disks 55 and 73, respectively, while the displacement of the spindle 52 furthermore results in the actuation of the change-over switch 97, whereby to connect the latter from its contact 97a to the contact 97b. As a consequence, the electric circuit of the electromagnet 96 is again closed via the brush 95c and the coupling motor started, whereby the machine effects another half revolution of the shaft 6 until the insulating segment 95d assumes a position opposite to the brush 950, thus arresting the machine with the needle in the upper dead center position.

During the foregoing renewed rotation, or operation of the machine from the initial lower to the upper dead center point position of the needle, the control disks 53 and 73 are each subjected to a half revolution, whereby, provided a proper design of the groove 54- of the disk 55, a pulling force is exerted upon the link 50 by the link 51 which, in turn, results in the rotation of the hollow shaft 46, FIG. 1, through gears 47, 48. Shaft 46 in turn rotates the rocking member 44 the pin 45 of which rotates the carrier 41 about the eccentric 42. As a consequence, the opening finger 40 acts to effect a simultaneous rotation of the bobbin case 21, via the stop member 23, in the direction opposite to the direction of rotation of the looptaker 20.

As a result of the rotation of the bobbin case 21, the bobbin thread 25, emerging from the opening 24 of the case and passing, in respect to the viewing direction as seen in FIG. 6, in front of the stop member 22 to the stitching hole in the stitching plate 33, is seized by the nose 37 of member 22 rotating together with the case 21 and led to the guide groove 3 of the member 22.

During the operation described hereinbefore, the needle thread 39 FIG. 7, is seized, during the upward movement of the needle, by the beak of the looptaker and drawn about the bobbin case 21, the latter being at rest during this movement of the looptaker by the stop member 22 engaging the stationary stop or abutment 35. As a consequence, the limb of the needle-thread loop extending to the preceding stitch in the work passes beneath the bobbin case 21, whereas the limb of the said loop extending to the needle 11 passes above the case 21. As the looptaker continues its rotation, the needle-thread loop drawn about the case 21 is cast off, that is, shortly upon passing the position shown in FIG. 7, whereupon the needle thread is withdrawn in the usual manner by the thread takeup device of the machine (not shown). As a consequence, the needle-thread loop passes the gap between the stop member 23 and the opening finger 40 so as to subsequently be seized by the nose 37 of the stop member 22, the latter having been rotated in the meantime, by the rotation of the case 21 by the finger 40, into the path of said loop, thereby causing the work limb of the needle loop 39 to enter the guide groove 38 of the member 22. As a result of the rotation of the bobbin case 21, the bobbin thread has been withdrawn to an extent sufiicient to cause the initiation of the next following stitch formation. At the same time, sufficient needle thread 39 is withdrawn by the stop member 22. The rotation of the member 22 furthermore causes a displacement of the two limbs of the threads 25 and 39 engaging the guide groove 38 in the direction of the thread cutter 90, whereby the needle limb of the needlethread loop 39 is split off from and maintained separate from the work limb portion of the loop.

Simultaneously with the rotation of the bobbin case 21, the end position of which is shown by FIG. 5, the lever 75 is deflected in accordance with the configuration of the groove 74 of the control disk 73, FIG. 3, whereby to lower the pull rod 83 by way of lever 81. Lowering of the pull rod 83 in turn causes the shearing parts 88, 89 of the cutter 90 to be deflected about the pin 91 in the direction of the threads 25, 39 by virtue of the identical design of the upper portions of the guide slots 86, 87, until the bobbin thread 25 and the work limb of the needle-thread loop 39 are positioned between the shearing blades 93, 94. During continued lowering of the rod 83, the shearing part 89, due to the now effective angular configuration of the slot 87 relative to the slot 86, is rotated about the pin 92, thus resulting in the blade 94 descending upon the blade 92 and trimming or severing the threads 25, 39. During the subsequent raising of the rod 83, the blades 93, 94 are again opened and the cutter returned to their normal or inoperative position.

Upon the subsequent release of the foot pedal or the like control member, after completion of the sewing operation, the fork 62, FIG. 1, is returned to its rest position, whereby the tension of the spring 72 will be relaxed and the spindle 52 returned towards the right or its initial rest position, to in turn disengage the guide pins 53 and 77 from their respective control disks 55 and 73.

Referring to the embodiment of the invention as applied to a double-chainstitch sewing machine shown by FIGS. 1l18, numeral 102 represents a drive shaft mounted below the bed or cloth plate 101 of the machine and driven by the main drive or armshaft through a belt or chain 103. Mounted upon shaft 102 is a gear 104 meshing with a counter-gear 106 secured to a further shaft journalled in a position parallel to the shaft 102. Shaft 105 carries an eccentric 107, FIGS. 13 and 14, embraced by apart 108 of a two-part eccentric rod 109. Jointed to the part 108, by the aid of a pin 110, is the second part 111 of the eccentric rod 109 the lower end of which forms a ball socket adapted to receive the spherical end 112 of a lever arm 114 fast upon the looptaker or hook carrier 113, FIG. 1. Exchangeably mounted upon the carrier 113 is a thread-carrying chainstitch looptaker or hook 115 disposed underneath the work feed device 116 indicated in dotted lines and serving to cooperate with the needle 117 for the formation of doublechainstitches in a manner well known.

The looptaker 113, FIGS. 13 and 14, is rotatively supported by a pivot pin 118 disposed in the fork-shaped end 119 of the looptaker bearing 120 fast on a lever arm 121. The latter is in turn jointed to an eccentric rod 122 embracing an eccentric 123 mounted upon shaft 102.

The looptaker bearing 120 is rotatively mounted upon a pin 124 which is secured to an oscillating member or support -126 mounted about a stationary pivot 125 on the frame of the machine. Member 126 is fitted with a guideway 127 engaged by a sliding block 128 which is rotatively supported upon a crank 130 secured to a rockshaft 129. A bent extension arm 131 of the member 126 carries an adjustable set screw 132 secured against accidental rotation by a nut 133.

A tension spring 135 mounted upon the rockshaft 129, FIGS. 11 and 13, and engaging the frame of the machine, on the one hand, and a setting ring fast upon shaft 129, on the other hand, serves to urge the member 129 to the position shown by FIG. 13 in which the screw 132 engages an abutment 136 on the frame of the sewing machine.

Secured to the free end of the rockshaft 129, FIG. 11, is a crank 137 which is jointed to a pull rod 138. The lower end of the latter may be connected to a foot pedal or the like control member (not shown). Secured to the bearing pin 124 is a setting ring 139 to prevent axial displacement of the looptaker bearing 120. Further secured to the pin 124 adjacent to the ring 139 is a lever arm 140 which has a bore 141 engaged by the spherical end of an arm 142 of a bellcrank lever 143. The latter is rotatively mounted, by means of a pivot screw 144, below the cloth plate 101. The remaining arm 145 of the lever 143 is of tubular construction and contains a longitudinally displaceable telescoping rod -146. A compression spring (not shown) disposed within the tubular arm 145 of the lever 143 acts to urge the rod 146 in the outward or upward direction.

The upper spherical-shaped end of the rod 145 engages a bore 147, FIG. 15, of a shearing element 148 of a scissors-like thread cutter 150 having a further cutting element 149 cooperating with the element 148. The element 148 of the cutter 150 is displaceably mounted between a pair of guide members 151 disposed upon a guide plate 152 which is secured to the underside of the cloth plate 101 of the machine. The shearing element 149 is rotatively mounted upon the element 148 by means of a pivot screw 153. Both elements 148 and 149 are fitted with cutting knives or blades 154, 155 adapted to cooperate in cutting the needle and looptaker threads 156 and 157 carried by the needle 117 (see also FIGS. 16-18) and the hook 115, respectively.

In order to produce cutting and opening movements of the shearing element 149 which frictionally engages the element 148 arranged for translatory movement between the guides 151, the element 149 is fitted with a lateral extension 158 in the path of which is disposed an abutment pin 159 secured to the guide plate 152, on the one hand, and an adjustable stop 161 mounted upon said plate by means of a set screw 160, on the other hand.

During the operation of the sewing machine, the looptaker 115 is subjected, in its operative position shown by FIGS. 11-13, to an oscillating movement for the seizing and casting off of the needle thread 156 applied by way of the shaft 102, gears 104, 106, the shaft 105, and eccentric 107 and eccentric rod 109 actuating the looptaker carrier 113. Besides, the needle-avoid movement of the looptaker 115 is applied by way of the shaft 102, the eccentric 123, eccentric rod 122, arm 121, and the looptaker bearing 120 rotatable about the pivot pin 124. The cooperation between both components of looptaker movement results in an elliptical operating path, in a manner well known in the operation of chainstitch sewing machines of the type shown and described herein.

In use, cutting of the needle thread 156 and of the looptaker thread 157 at the end of a seam being sewn is initiated by stopping the machine in the manner known and described hereinbefore with the needle 117 being automatically positioned in the upper dead center position, whereby the loop taker 115 assumes a position as shown by FIG. 16, that is, coinciding with the position at the end of the thread-seizing or forward movement during an operating cycle. In this position, the needle-thread loop 156 embraces the looptaker hook in the manner shown in the drawing.

Upon subsequent depression of the foot pedal (not shown), the pull rod 138, FIG. 11, is rotated by the crank 137 against the action of the torsion spring 135'. As a consequence, the slide block 128 in the guide 127 acts to rotate the member 126 about its stationary pivot 12 from the position shown in FIG. 13 to the position shown in FIG. 14. Due to this rotation of the member 126 and the resultant increase of the spacing distance between the pivot pin 124 and the shaft 102, the knuckle-joint connecting the eccentric rod 122 with the arm 121 of the looptaker bearing is stretched, in such a manner as to cause the looptaker bearing 120 supporting the carrier 113 of the looptaker 115 to displace the latter from its normal operative position, FIG. 13, to the thread-cutting position, FIG. 14.

Besides, the increase of the spacing distance between the pin 118, FIG. 11, and the pin 110 of the eccentric rod 109, also resulting from the rotation of the member 126, causes the knuckle-joint connecting the lever arm 114 and the part 111 of the eccentric rod 109 to be stretched somewhat, whereby to displace the carrier 113 and with it the looptaker 115 to a slight extent in the direction of its loop-seizing or forward movement.

As a consequence, the looptaker assumes a final position at the end of its three-fold thread-withdrawing movement as shown in FIG. 18, wherein the looptaker hook has been deflected, as a result of saidmovement, in the forward and downward direction, in such a manner as to extract sufiicient lengths of both the needle and looptaker threads 156 and 157. respectively, to ensure the safe initiation of the next following stitch formation.

At the same time, rotation of the member acts to retract the loop taker 115 from the path of the thread cutter 150, as well as to enlarge or extend the loop of the needle thread 156, to thereby ensure a safe engagement of the cutter 150 with the thread 157, on the one hand, and with the limb of the needle-thread loop 156 leading to the needle 117, on the other hand.

Simultaneously, with the thread-withdrawing operation of the looptaker 115, the rotation of the bearing pin 124 causes a rotation of the lever arm secured to said pin, whereby to operate the cutter along the guide 151 by way of the lever 143 and telescope rod 146, to its cutting position as shown by FIG. 17.

In the position according to FIG. 18, showing the relation of the looptaker and cutter immediately prior to the thread-cutting operation, the shearing blades 154 and 155 have already seized both the looptaker thread 157 and the needle limb of the needle-thread loop 156. During continued displacement of the cutter 150, the blade 155 of the shearing element 149, upon engagement of the extension 159 with the pin 159, is rotated towards the blade 154, whereby to effect final cutting of the threads 156 and 157.

After release of the foot pedal at the end of the thread cutting operation, the member 126 is returned as a result of the action of the spring 135, to its starting position by the set screw 132 engaging the abutment 136. During this operation, the looptaker 115, together with its operation parts, is returned to the normal or sewing position, FIGS. 1l-13, the same applying to the cutter 150. The extension 159 of the shearing element 149 engages, during the cutter return movement, the stop 161, to thereby result in the opening and return of the cutter to its inoperative or starting position.

As will be understood, operation of the thread cutter by the foot pedal or the like control member may also be initiated during or prior to the end of the sewing operation by temporarily storing the control operation by a spring, in the manner described hereinbefore in connection with the embodiment of the invention according to FIGS. 1-10.

In the foregoing the invention has been described in reference to specific illustrative devices or embodiments. It will be evident, however, that variation and modifications, as well as the substitution of equivalent parts for those shown for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

I claim:

(2) first operating mechanism to consecutively operate said cutter from said inoperative position to an operative thread-cutting position and to actuate said cutting elements upon arrival in said operative position,

(3) second operating mechanism including control means therefor to operate said looptaker element from said predetermined position to a retracted position, to extract a predetermined length of looptaker thread, and

(4) coupling mechanism between said first and said second operating mechanism, to operate said cutter towards the thread being extracted and to seize and cut the extracted thread by said elements of said cutter upon the actuation of said control means.

2. In thread-cutting apparatus as claimed in claim 1, said cutter in the retracted position being obstructed by said looptaker element in operative position.

3. In thread-cutting apparatus as claimed in claim 1, including means to disable said control means upon actuation during operation of said machine and to restore its effectiveness upon stoppage of said machine.

4. In thread-cutting apparatus as claimed in claim 1, wherein said looptaker is of the rotary double-lockstitch type frictionally enclosing a bobbin case having an open ing passing the looptaker thread and being restrained against rotation by said looptaker by a stationary abutment engaging a stop upon said case, said looptaker further comprising an intermittently operated opening finger engaging said case, to open the needle-thread escape gap between said abutment and said stop at predetermined points during a stitching cycle, said bobbin case forming said operative looptaker element being mounted for rotation to a predetermined position in a direction opposite to the direction of rotation of said looptaker, and coupling means connecting said second operating mechanism with said finger.

5. In thread-cutting apparatus as claimed in claim 1, wherein said looptaker is of the double-chainstitch type having a thread-carrying looptaker hook, with means to oscillate the same through an elliptical path, for the production of needle-thread seizing and casting off as well as needle-avoid movements, and said machine includes means to automatically stop the same in the upper dead center needle position, whereby to cause said looptaker hook to embrace the needle thread loop and thereby to extract, during operation of said second operating mechanism, both the needle and looptaker threads and to present the same to the elements of said cutter.

6. In thread-cutting apparatus as claimed in claim 1, wherein said looptaker is the rotary double-lockstitch type frictionally enclosing a bobbin case having an opening passing the looptaker thread and restrained against rotation by the looptaker by a stationary abutment engaging a stop upon said case, said bobbin case forming said operative looptaker element being mounted for rotation to a predetermined position in a direction opposite to the direction of rotation of said looptaker.

7. In thread-cutting apparatus as claimed in claim 6, including guide means carried by said bobbin case, to catch and present the extracted thread to said elements of said cutter.

8. In thread-cutting apparatus as claimed in claim 6, including guide means carried by said bobbin case, further means synchronized with said first and second operating mechanisms, to operate, upon stoppage of said machine, said needle from its lower dead center position to its upper dead center osition, to draw and cast a needle-thread loop about said looptaker, said guide means adapted to catch the extracted looptaker thread and the work limb of the cast-01f needle-thread loop and to present both threads to said elements of said thread cutter for simultaneous cutting thereby.

9. In thread-cutting apparatus as claimed in claim 6, including stoppage means synchronized with said first and second operating mechanisms, to alternately arrest the sewing machine in the lower and upper dead center positions, said bobbin case including a thread guide, whereby operation of said control means initiating the retraction of said looptaker element and operation of said cutter acts to operate the sewing machine from its normally lower dead center position to the upper dead center position, to draw and cast off a needle-thread loop about said looptaker simultaneously with the extraction of the looptaker thread and the work limb of the cast-off needle-thread loop and to present both threads to said elements of said cutter for simultaneous cutting thereby.

References Cited UNITED STATES PATENTS 1,291,335 1/1919 Wood 112-252 1,346,814 7/1920 Fifield 112-252 2,294,471 9/1942 Lyons 112--252 X 3,176,639 4/1965 Kleemann et al. 112-252 X 3,211,117 10/1965 Spetchermann et al. 112252 HERBERT F. ROSS, Primary Examiner. 

1. THE COMBINATION WITH A SEWING MACHINE INCLUDING A RECIPROCATORY NEEDLE CARRYING A NEEDLE THREAD PASSING THROUGH AN OPENING OF SAID NEEDLE, A LOOPTAKER HAVING AN OPERATIVE ELEMENT CARRYING A LOOPTAKER THREAD PASSING THROUGH AN OPENING OF SAID ELEMENT, SAID ELEMENT HAVING A PREDETERMINED OPERATIVE POSITION DURING THE OPERATION OF SAID MACHINE IN PRODUCING A STITCH IN THE WORK BEING OPERATED ON BY COOPERATION OF SAID NEEDLE WITH SAID LOOPTAKER, OF THREAD-CUTTING APPARATUS COMPRISING IN COMBINATION: (1) A THREAD CUTTER INCLUDING A PAIR OF CUTTING ELEMENTS AND POSITIONED NORMALLY IN AN INOPERATIVE RETRACTED POSITION, (2) FIRST OPERATING MECHANISM TO CONSECUTIVELY OPERATE SAID CUTTER FROM SAID INOPERATIVE POSITION TO AN OPERATIVE THREAD-CUTTING POSITION AND TO ACTUATE SAID CUTTING ELEMENTS UPON ARRIVAL IN SAID OPERATIVE POSITION, (3) SECOND OPERATING MECHANISM INCLUDING CONTROL MEANS THEREFOR TO OPERATE SAID LOOPTAKER ELEMENT FROM SAID PREDETERMINED POSITION TO A RETRACTED POSITION, TO EXTRACT A PREDETERMINED LENGTH OF LOOPTAKER THREAD, AND (4) COUPLING MECHANISM BETWEEN SAID FIRST AND SAID SECOND OPERATING MECHANISM, TO OPERATE SAID CUTTER TOWARDS THE THREAD BEING EXTRACTED AND TO SEIZE AND CUT THE EXTRACTED THREAD BY SAID ELEMENTS OF SAID CUTTER UPON THE ACTUATION OF SAID CONTROL MEANS. 